must meaning
EN
[mʌst] [məs(t)] [-ʌst] 
US WMust
- Must (from the Latin vinum mustum, “young wine”) is freshly pressed fruit juice (usually grape juice) that contains the skins, seeds, and stems of the fruit.
- NounPLmusts
- Something that is mandatory or required.
- If you'll be out all day, a map is a must.
- The property of being stale or musty.
- Something that exhibits the property of being stale or musty.
- Fruit juice that will ferment or has fermented, usually grapes.
- A time during which male elephants exhibit increased levels of sexual activity and aggressiveness (also spelled musth).
- An elephant in this sexual and aggressive state.
- Something that is mandatory or required.
- VerbSGmustsPRmustingPT, PPmusted
- (modal auxiliary, defective) To do with certainty; indicates that the speaker is certain that the subject will have executed the predicate.
- If it has rained all day, it must be very wet outside.
- You picked one of two, and it wasn't the first: it must have been the second.
- The children must be asleep by now.
- (modal auxiliary, defective) To do as a requirement; indicates that the sentence subject is required as an imperative or directive to execute the sentence predicate, with failure to do so resulting in a negative consequence.
- You must arrive in class on time. — the requirement is an imperative
- This door handle must be rotated fully. — the requirement is a directive
- Arise, and go into the city, and it shall be told thee what thou must do. (Bible, Acts 9:6)
- (transitive) To make musty.
- (intransitive) To become musty.
- (modal auxiliary, defective) To do with certainty; indicates that the speaker is certain that the subject will have executed the predicate.
- More Examples
- Used in the Middle of Sentence
- To acquire a right of way by long use, a claimant must show use as of right, peaceably, openly and without permission
- A future state must needs subvene to prevent the whole edifice from falling into ruin. — Bishop Warburton.
- I must alert you all to a critical oversight in today's slashfic. Amid all the gleeful anal romping and glute-grinding cock-milking, where, o where, is the santorum?
- Used in the Beginning of Sentence
- Must our Aldersgate experience help us meet the needs of common men ?
- Used in the Middle of Sentence
Definition of must in English Dictionary
- Part-of-Speech Hierarchy
- Nouns
- Countable nouns
- Countable nouns
- Verbs
- Auxiliary verbs
- Modal verbs
- Modal verbs
- Defective verbs
- Intransitive verbs
- Transitive verbs
- Verbs by inflection type
- Irregular verbs
- Defective verbs
- Defective verbs
- Irregular verbs
- Auxiliary verbs
- Nouns
Source: Wiktionary
Grammatically, this word "must" is a noun, more specifically, a countable noun. It's also a verb, more specifically, an auxiliary verb, a defective verb, an intransitive verb, a transitive verb and a verbs by inflection type.